Oshi no Ko Wiki
Episode 1 4
"It's a secret~"
This article contains SPOILERS to later chapters. Read this page at your own risk.

Life is about doing what you want to do! If you keep talking cost this return, you won't accomplish anything! Life can end before you get a chance to accomplish anything; it happens.

― Ruby Hoshino

Ruby Hoshino (ほし) () () () () , Hoshino Rubii?」, more commonly referred to as just Ruby「ルビー, Rubī?」, is the female protagonist and one of the titular characters of Oshi no Ko. In her previous life, she was known as Sarina Tendouji, a terminally ill patient who was cared for by Gorou Amamiya and, following her death, was reincarnated as the child of her favorite idol, Ai Hoshino.

Neglected by her parents in her previous life and being a fan of Ai, she greatly enjoyed her new life, with her new mother teaching her how to be an idol from an early age. Unfortunately, this happy life ended when Ai was murdered by a deranged fan. Afterward, determined to fulfill her mother's dreams, she reformed Ai's idol group with the support of her friends.

Spoilers Ahead!

She later undergoes a great change after learning that Gorou was killed by the same individual who murdered her mother, prompting her to resort to unsavory methods to quickly rise to fame and draw out the culprit. However, she ultimately gives up on revenge upon learning that Gorou was beside her all along.


Main article: Ruby Hoshino/Gallery

Ruby is a beautiful young girl of average height with blonde hair that she ties in a side ponytail (much like how her late mother Ai Hoshino does) and possesses pink-ruby colored eyes with a six-star on her left eye like her late mother.

Ruby has been stated to resemble Ai by many people, such as Aqua Hoshino and Kana Arima where Kana herself confirmed that her keen nose in industry "can sense potential in this girl" and it reminds her of Ai. The resemblance grows stronger when she wears a purple wig, to the point that it shocks others especially Akane Kurokawa.


In her past life, Ruby was a frail girl who died of anaplastic astrocytoma and could barely walk a few steps without stumbling. Now overwhelmed with joy as Ruby Hoshino, the daughter of her favorite idol, Ai Hoshino, takes her life to the fullest, Ruby has given herself the goal of becoming an idol singer, not only to follow in her mother's footsteps, but also to fulfill her promise to Gorou Amamiya. Unbeknownst to her, Gorou had already passed away and been reborn as her older twin brother, Aqua Hoshino.

Unlike Aqua who is calm, calculated and discreet, Ruby is the polar opposite of him as she is extroverted, outgoing, loud, optimistic and communicative compared to her brooding brother. She is most apparent in the connections she makes with others. At the same time, Aqua only does this to further his agenda. She doesn't share her brother's opinion of hunting down the culprit who killed their mother, instead moving on from that incident and focusing on her dreams. She persists in this notion to the point where she often conflicts with her brother's interests.

Ruby tends to speak her mind without a filter, often referring to Kana Arima as the "gourd girl" and the "girl who will lick a lying snitch," much to Kana's displeasure. Additionally, Ruby has utilized the "airhead sister" persona to her advantage in the media as a character she created to promote herself.

She is the biggest defender of her mother Ai's secrecy and reputation.

Spoilers for Later Chapters!

Following the discovery of Gorou's corpse and learning that his and Ai's murders correlate with each other during the trip to Takachiho, Ruby's drive for revenge becomes a lot more intense, and comparatively more aggressive, albeit stealthily so, than even Aqua's. The murderer stole the future she wanted, and so did Gorou's; she resolved to ensure Gorou gets justice, even if it meant using her brother, who finally attained true happiness with Akane Kurokawa.[10]

Ruby reveals herself to be just as methodical and cunning as her brother. After her darker turn in the manga for the sake of her revenge, Ruby adopts a two-faced attitude towards others entirely whenever she sees that she could benefit from them in the long run:

  • She acts friendly and affable with Meiya, but secretly disdains her despite being shown to get along well with her, knowing that Meiya likes beef and vents her frustrations on Twitter.
  • She also made sure that she had Tetsu Urushibara under her thumb during the Dig Deep arc by manipulating him into believing that she had saved him and his job through a scandal that she had caused in secret for her own benefit.
Spoilers for Later Chapters!

After Aqua reveals their mother's secret to the public, Ruby has a temporary break with her relationship with her twin brother because she hates him so much that he kept it from her. She is very honest to the extreme with herself and hates lies.


Skills & Talents[]

Ruby's greatest asset has repeatedly been noted to be her natural beauty, which she inherited from her mother Ai Hoshino. Kana Arima also claimed that she has a charisma about her that draws people in. In addition, her mother taught her how to dance from an early age and even Aqua Hoshino noted that she indeed possessed a natural talent. However, Ruby lacked in arguably the most vital area for being an idol: singing; only scoring a mediocre 38 at karaoke. She also held herself back by refusing to resort to any underhanded tactics, causing Minami Kotobuki to believe that Ruby was too "pure" for the cutthroat entertainment industry.

Spoilers for Later Chapters!

Due to her initially trying to emulate Ai, Anemone Monemone noted that Ruby lacked her own passion, which prevented her from reaching her full potential. However, upon learning of Gorou Amamiya's death and resolving to avenge him, she began to radiate a murderous aura that drew people's interest. She also threw away her initial naivete and started using any means necessary to quickly rise in fame. In a way, she showed herself to be just as manipulative as Aqua, if not more so, since she was not just benefitting from scandals but actively causing them. Over time, her singing ability also improved substantially with it now rivalling Kana and Mem-Cho's.

In addition to her fame as an idol, Ruby also had a budging talent for acting, with Aqua believing that she was a more skilled performer than himself when they were children. Even Akane Kurokawa, a professional actress, was quick to recognize Ruby's talent after just a single rehearsing session together. Although inexperienced, Taishi Gotanda chose her for the starring role in his film, The 15 Year Lie, and he used the opportunity to coach her in acting, causing her talent to quickly blossom with a lot of room left over to develop further.


Stars Entertainer Singing Acting Popularity Internet/Social Media Variety
★★★★☆ A B D S B B







Manga Appearance[]

Prologue: Childhood
Chapter 1: Mother & Children Debut
Chapter 2: Big Brother & Little Sister Appears
Chapter 3: Babysitter Appears
Chapter 4: How to Smile Appears
Chapter 5: Director & Actress Appears
Chapter 6: Child Actors Appears
Chapter 7: If You Fear Falling, You'll Fall Harder Appears
Chapter 8: Ai Hoshino Part 1 Appears
Chapter 9: Ai Hoshino Part 2 Appears
Chapter 10: Introduction Appears
Show Business
Chapter 11: Audition Appears
Chapter 12: The Third Option Appears
Chapter 13: Procedures Appears
Chapter 14: Connection Appears
Chapter 15: The Manga Drama Appears
Chapter 16: Acting Skills Absent
Chapter 17: Staging Absent
Chapter 18: Modest Praise Appears
Chapter 19: The Entertainment Department Appears
Chapter 20: New Member Appears
Dating Reality Show
Chapter 21: The Dating Reality Show Appears
Chapter 22: Wannable Idol Appears
Chapter 23: AMark Appears
Chapter 24: Egosearch Appears
Chapter 25: Up in Flames Absent
Chapter 26: Storm Appears
Chapter 27: Viral Absent
Chapter 28: Role Creation Absent
Chapter 29: Perfect Copy Appears
Chapter 30: The First Mentioned
Chapter 31: Love for Real Absent
Chapter 32: Appropriate Age Appears
The First Concert
Chapter 33: Motivation Appears
Chapter 34: Center Appears
Chapter 35: Responsible Appears
Chapter 36: The Night Before Appears
Chapter 37: Pressure Appears
Chapter 38: Group Fan Appears
Chapter 39: A Job That's Kinda Fun Appears
Chapter 40: Sore Loser Appears
2.5D Stage Play
Chapter 41: Introductions Appears
Chapter 42: Read-Through Absent
Chapter 43: The Losing Heroine Absent
Chapter 44: The Visit Absent
Chapter 45: The Telephone Game Absent
Chapter 46: Theater Absent
Chapter 47: Studio Visit Absent
Chapter 48: Crunch Time Absent
Chapter 49: Rewriting Absent
Chapter 50: Emotional Acting Flashback
Chapter 51: Inquiry Flashback
Chapter 52: Boyfriend, Girlfriend Absent
Chapter 53: Playboy Appears
Chapter 54: Axis of a Conflict Flashback
Chapter 55: Opening Appears
Chapter 56: Beginning of Competition Absent
Chapter 57: Lousy Absent
Chapter 58: Growth Absent
Chapter 59: Admiration Absent
Chapter 60: The Sun Imagined
Chapter 61: Play Along Absent
Chapter 62: Ad-lib Absent
Chapter 63: Genius Actor Appears
Chapter 64: Trigger Absent
Chapter 65: Regret Flashback
Chapter 66: The Curtain Falls Appears
Chapter 67: Drinking Party Absent
Chapter 68: Liberation Appears
Chapter 69: Room Tour Appears
Chapter 70: Flame Appears
Chapter 71: Pedestrian Bridge Appears
Chapter 72: Freedom Appears
Chapter 73: Smart Absent
Chapter 74: Takachiho Appears
Chapter 75: Mother and Mother Absent
Chapter 76: Music Video Appears
Chapter 77: Reunion Appears
Chapter 78: Use Appears
Chapter 79: Duty Appears
Chapter 80: Wish Appears
Chapter 81: Rapid Progress Appears
Chapter 82: B-Komachi Night Appears
Chapter 83: Obsessed Flashback
Chapter 84: Hard Selling Appears
Chapter 85: Calculation Appears
Chapter 86: AD Appears
Chapter 87: Lies Appears
Chapter 88: Offer Appears
Chapter 89: Cosplay Appears
Chapter 90: Compliance Appears
Chapter 91: Dig Deep Appears
Chapter 92: Ritual Purification Appears
Chapter 93: Leak Appears
Chapter 94: Breakthrough Appears
Chapter 95: Blindness Imagined
Chapter 96: White Roses Flashback
Chapter 97: Together Absent
Chapter 98: Going Astray Absent
Chapter 99: Drinking Appears
Chapter 100: Industry Appears
Chapter 101: Predicament Absent
Chapter 102: Idol and Love Appears
Chapter 103: Scandal Absent
Chapter 104: Countermeasure Appears
Chapter 105: Reporter Appears
Chapter 106: Breaking Off Appears
Chapter 107: Friends Mentioned
Chapter 108: Plan Appears
Chapter 109: Night Absent
Chapter 110: How It Began Imagined
Chapter 111: Mammon-Worship and Passion Flashback
Chapter 112: Towards the Future Appears
Chapter 113: Commercial Work Absent
Chapter 114: Interpersonal Audition Appears
Chapter 115: Roles Appears
Chapter 116: Responsibility Appears
Chapter 117: Panda Pictured
Chapter 118: Activation Absent
Chapter 119: Biological Mother Appears
Chapter 120: Lack of Ability Appears
Chapter 121: Sarina Tendouji Appears
Chapter 122: Doc Appears
Chapter 123: Bad Move Appears
Chapter 124: Reversal Appears
Chapter 125: Dazzled Absent
Chapter 126: Management Appears
Chapter 127: Scouting A Girl Appears
Chapter 128: Script Reading Appears
Chapter 129: Piece Appears
Chapter 130: Basic Tactic Absent
Chapter 131: Atonement Appears
Chapter 132: Nino Appears
Chapter 133: Acting Appears
Chapter 134: Depths Appears
Chapter 135: By Her Side Appears
Chapter 136: Fight Appears
Chapter 137: Idol Appears
Chapter 138: Amends Appears
Chapter 139: Lookism Appears
Chapter 140: Is This Right? Appears
Chapter 141: Chain Appears
Chapter 142: Responsibility Appears
Chapter 143: Blind Follower Appears
Chapter 144: Fan of the Originals Appears
Chapter 145: Children Appears
Chapter 146: Role Appears
Chapter 147: Wish Appears
The End of the Play
Chapter 148: End of Summer Appears
Chapter 149: By the Sea Appears
Chapter 150: Knife Imagined
Chapter 151: Catch Ball Appears
Chapter 152: Interview Appears
Toward the Stars and Dreams
Chapter 153: Fiction Flashback
Chapter 154: 15-Year Lie Appears
Chapter 155: Happy End Appears
Special Chapter Appears
Interlude Chapter 1 Absent
Interlude Chapter 2 Absent
Interlude Chapter 3 Absent
Interlude Chapter 4 Appears

Anime Appearance[]

Season 1
Episode 1: Mother and Children Debut
Episode 2: Third Option Appears
Episode 3: Manga Based TV Drama Appears
Episode 4: Actors Appears
Episode 5: Reality Dating Show Appears
Episode 6: Egosurfing Appears
Episode 7: Buzz Appears
Episode 8: First Time Appears
Episode 9: B-Komachi Appears
Episode 10: Pressure Appears
Episode 11: Idol Appears
Season 2
Episode 12: Tokyo Blade Appears
Episode 13: The Telephone Game Absent
Episode 14: Rewriting Appears


  • The name Ruby means "lapis lazuli" (瑠) (ru), "beautiful" (美) (mi/bi) and "clothing, garment" (衣) (i).
    • Just like Aquamarine, Ruby is a gemstone that is known for it's red coloring.
    • Just like her older twin brother Aqua Hoshino, Ruby's name is a reference to her eye color.
  • Ruby's surname Hoshino means "star" (星) (hoshi) and "field, wilderness" (野) (no).


  • Ruby's mother, Ai Hoshino, has one star in each eye; Ruby inherited a star in her left eye and her brother Aqua Hoshino inherited it in his right eye.
    • Her star later becomes blackened and she gains an additional black star in her right eye after revolving around use dirty tactics to rise in the entertainment industry.
  • Ruby wants to be an idol like Ai once was.
  • Ruby once pretended to be Amaterasu, the goddess of the sun in Japanese mythology.[14] While the scene is played as a joke at the time, it is later revealed that she and Aqua died (in their past lives) and reborn in the town of Takachiho in Miyazaki prefecture. And as Akane Kurokawa explained during that chapter, Takachiho is where Amaterasu once shut herself in.[15]
    • If Ruby is interpreted to be based on Amaterasu, then Aqua would be based on one of Amaterasu's siblings, likely to be based on Susanoo.
  • Ruby's height is 158 cm [1], making her the tallest B-Komachi member (compared to Kana Arima's 150 cm and Mem-Cho's 155 cm).
  • Ruby applied to be an idol at 14, but she was rejected and had to wait two years before applying again. [16]
  • Ruby is in Class 1-F during her first year [17] and in Class 2-F during her second year [18] at Youtou High School.
  • Ruby starts high school at 16.[6]
  • Ruby's glowstick idol color is red, which is the same color as Ai.[19]
  • Kaguya Shinomiya from Kaguya-sama: Love is War has interacted with Ruby, taking photos of the latter as a part of a job. [20]


  1. The twins' age during the filming of That Was the Start was never outright stated, but it can be inferred that they are at least one year old from available information.


  1. 1.0 1.1 Oshi no Ko Official Anime Website: TALENT -アニメ『【推しの子】』公式サイト- (in Japanese).
  2. Oshi no Ko Manga: Ch. 2 (p. 4).
  3. Oshi no Ko Manga: Ch. 5 (p. 2).
  4. Oshi no Ko Manga: Ch. 7 (p. 3).
  5. Oshi no Ko Manga: Ch. 11 (p. 2).
  6. 6.0 6.1 Oshi no Ko Manga: Ch. 23 (p. 10).
  7. Oshi no Ko Manga: Ch. 84 (p. 8).
  8. Oshi no Ko Manga: Ch. 100 (p. 6), Kana is 18 before going off to meet the director and Ruby is 1 year younger than Kana.
  9. Oshi no Ko Manga: Ch. 117 (p. 7), it has been two years since Aqua asked Kana to become an idol.
  10. Oshi no Ko Manga: Ch. 79.
  11. Oshi no Ko Manga: Ch. 106.
  12. 12.0 12.1 Oshi no Ko Anime: Ep. 11.
  13. Oshi no Ko Manga: Ch. 74 (p. 1).
  14. Oshi no Ko Manga: Ch. 3 (p. 16).
  15. Oshi no Ko Manga: Ch. 74.
  16. Oshi no Ko Manga: Ch. 11.
  17. Oshi no Ko Manga: Ch. 19 (p. 1).
  18. Oshi no Ko Manga: Ch. 87 (p. 9).
  19. Oshi no Ko Manga: Ch. 38 (p. 4).
  20. Oshi no Ko Manga: Special Chapter.


Ichigo Production, Inc
Talent Ai HoshinoTakamineFuyuko NiinoWatanabeMeimeiAriKyun
Independent Aqua HoshinoPieyon
Graduates / Students Kana ArimaAqua HoshinoRuby HoshinoFrill ShiranuiMinami Kotobuki
Current Members Akane KurokawaTaiki HimekawaToshirou Kindaichi (Founder)
Former / Graduates
That Was the Start
Cast Ai HoshinoKana ArimaAqua Hoshino
I'll Go With Sweet Today
Cast Kana ArimaMelt NarushimaAqua Hoshino
Author Yoriko Kichijouji
We're About to Fall in Love for Real
Cast Yuki SumiAkane KurokawaMem-Cho
Aqua HoshinoNobuyuki KumanoKengo Morimoto
Tokyo Blade
Cast Taiki HimekawaKana ArimaMelt Narushima
Akane KurokawaAqua HoshinoSakuya Kamoshida
Author Abiko Samejima
Dig Deep! One Chance
Cast Aqua HoshinoRuby HoshinoKana Arima
The 15 Year Lie
Major Roles Ai HoshinoHikaru KamikiAiri Himekawa
Fuyuko NiinoGorou AmamiyaSeijuro Uehara
Crew Taishi Gotanda (Screenplay, Director)Masaya Kaburagi (Producer)